Preliminary Study On In Vitro And In Vivo Anti-infective Role Of Vitamin D

At the end of the twentieth century, ultraviolet light was successfully used to treat tuberculosis of the skin. It is confirmed that upper respiratory tract infections had been inversely associated with sun exposure. During the last decade, basic scientific research demonstrated that vitamin D has an important anti-infective role. In this study, we investigated anti-infective role of vitamin D in vitro and in vivo.Objective: Lipopolysaccharide(LPS) and staphylococcus aureus(SA) were used to stimulate RAW264.7 cells in an attempt to assess macrophage host defense regulated by 1,25(OH)2D3. Furthermore, LPS was intravenously administrated to C57/BL mice to study the effects of 1,25(OH)2D3 on the survival and acute lung injury(ALF) induced by LPS in vivo. To explore the relationship between lung infection and of vitamin D metabolites in population, a case-control study was conducted in Diabetes Mellitus.Methods: (1) Mouse RAW264.7 macrophages were cultured in Dulbecco's modified Eagle's medium (DMEM) containing 10% FBS. 1,25(OH)2D3 was added to the media at the 10-8 mol/L final concentration . After 24 hours culture, the cells were then exposed to 1μg/ml of LPS or SA at a ratio of 1:100 and incubated for 1, 3 and 6h. The phagocytosis, intracellular reactive oxygen species(ROS) release, mitochondrial membrane potential(MMP), intracellular free calcium concentration [Ca2+]i and apoptotic percentage in macrophages were investigated by flow cytometry(FCM). (2) C57/BL mice was administrated 1,25(OH)2D3 intravenously for a week. Then, the mice were challenged with intravenous LPS to establish animal models with acute lung injury. Tumor necrosis factor-α(TNF-α) contents in serum, heart and lung tissues were measured by ELISA. The survival rate and pulmonary edema were also studied in the mice. (3) A small population of 49 lung infection and 116 controls was investigated to find the relative risk of lung infection in Diabetes Mellitus. The information about sex, age, the levels of fast glucose, glycated hemoglobin A1c, 25(OH) D3 and 1,25(OH)2D3 in serum were retrieved.Results: (1) 1,25(OH)2D3 significantly decreased macrophage apoptosis induced by LPS(P<0.05). 1,25(OH)2D3 significantly increased MMP and ROS at earlier and decreased MMP and ROS at later(P<0.05). (2) After SA infection, the macrophage phagocytic activity in 1,25(OH)2D3 added group was significantly increased at 1h(P<0.01) and decreased at 6h(P<0.01). ROS release in 1,25(OH)2D3 added group was significantly increased at 1h(P<0.01) while decreased at 3h and 6h(P<0.01). (3) After mice challenged with intravenous LPS, the half of survival time(T1/2) were 65h and 100.5h in 1,25 (OH)2D3 added group and LPS group respectively. The Wet/Dry of lung in 1,25(OH)2D3 added group was significantly decreased compare to that in LPS group. (4) The ratio of vitamin D deficiency in case was significantly increased compared to that in control.Conclusion: (1) 1,25(OH)2D3 inhibited macrophages apoptosis induced by LPS and SA; 1,25(OH)2D3 increased macrophage phagocytic activity. (2) 1,25(OH)2D3 decreased pulmonary edema and increased survival time in a model of acute lung. (3) Vitamin D deficiency may be prone to pulmonary infection in diabetes.